After 20 years of development, the energy density of the lithium-ion battery has been promoted greatly, but now the promotion of energy density runs into the bottleneck. The acceleration of the battery charging speed in limited energy density can effectively improve user experience. Hence, the fast charge lithium-ion battery with high energy density will stand out from the future competition.
On the premise of holding high energy density, to improve the charging speed of lithium-ion battery, lithium-battery researchers have done a lot work by changing electrode active material and current collector, and optimizing electrolyte component. These works have improved the battery fast charge performance greatly. But along with the improvement, the cost of battery raises and the related technology becomes more complex. On the basis of unchanging the ingredients and the structure, the performance of lithium battery can be optimized by adjusting the charged conditions.
The present charging method is that the battery is charged continuously with a constant current to a certain potential, and then the battery is charged with constant voltage at the certain potential. This method will make the cathode potential constantly increasing and the anode potential constantly decreasing. When the anode potential is lower than 0V, lithium ion will be reduced to lithium metal, liberated at the anode surface. Especially at low temperature, due to the decrease of the ion conductivity and the electron conductivity of lithium battery, the polarization degree will increase in charging process. The sustained charging method will make the polarization phenomenon more obvious, increasing the probability of the liberation of lithium. And the accumulation of lithium dendritic crystal on the electrode surface will pose a big threat to the safety performance of battery.